Systems and methods for monitoring blowout preventer equipment

ABSTRACT

A system for a blowout preventer (BOP) stack assembly includes one or more pairs of ultrasonic transducers coupled to a body that is configured to support a movable component of the BOP stack assembly, wherein each pair of ultrasonic transducers comprises a first ultrasonic transducer disposed on a first side of the body and a second ultrasonic transducer disposed on a second side of the body, opposite the first side. The system also includes a controller configured to receive a first signal indicative of a position of the movable component from the one or more pairs of ultrasonic transducers, to determine the position of the movable component based on the first signal, and to provide a first output indicative of the position of the movable component.

BACKGROUND

This section is intended to introduce the reader to various aspects ofart that may be related to various aspects of the present invention,which are described and/or claimed below. This discussion is believed tobe helpful in providing the reader with background information tofacilitate a better understanding of the various aspects of the presentinvention. Accordingly, it should be understood that these statementsare to be read in this light, and not as admissions of prior art.

A blowout preventer (BOP) stack is installed on a wellhead to seal andcontrol an oil and gas well during drilling operations. A drill stringmay be suspended inside a drilling riser from a rig through the BOPstack into the well bore. During drilling operations, a drilling fluidis delivered through the drill string and returned up through an annulusbetween the drill string and a casing that lines the well bore. In theevent of a rapid invasion of formation fluid in the annulus, commonlyknown as a “kick,” the BOP stack may be actuated to seal the annulus andto control fluid pressure in the wellbore, thereby protecting wellequipment disposed above the BOP stack. However, current BOP systems maynot effectively monitor components of the BOP stack.

BRIEF DESCRIPTION OF THE DRAWINGS

Various features, aspects, and advantages of the present invention willbecome better understood when the following detailed description is readwith reference to the accompanying figures in which like charactersrepresent like parts throughout the figures, wherein:

FIG. 1 is a schematic diagram of an offshore system in accordance withan embodiment of the present disclosure;

FIG. 2 is a perspective view of an embodiment of a BOP stack assemblythat may be used in the offshore system of FIG. 1;

FIG. 3 is a cross-sectional top view of a portion of a BOP of the BOPstack assembly of FIG. 2, wherein a ram is in an open position;

FIG. 4 is a cross-sectional top view of the portion of the BOP of FIG.3, wherein the ram is in a closed position;

FIG. 5 is a cross-sectional top view of a portion of a BOP of the BOPstack assembly of FIG. 2 having phased array ultrasonic transducers;

FIG. 6 is a cross-sectional side view of a portion of a BOP of the BOPstack assembly of FIG. 2 having phased array ultrasonic transducersextending axially along the BOP;

FIG. 7 is a top view of a portion of the BOP stack assembly of FIG. 2having slots configured to support ultrasonic transducers;

FIG. 8 is a side view of the portion of the BOP stack assembly of FIG. 8having the slots configured to support the ultrasonic transducers;

FIG. 9 is a schematic diagram of an embodiment of a system configured tomonitor a position of a movable component of the BOP stack assembly ofFIG. 2;

FIG. 10 is a flow diagram of an embodiment of a method for monitoring aposition of a movable component of the BOP stack assembly of FIG. 2;

FIG. 11 is a flow diagram of an embodiment of a method for monitoring acondition of a seal of a ram of the BOP stack assembly of FIG. 2;

FIG. 12 is a flow diagram of an embodiment of a method for monitoring atubular string extending through a bore of the BOP stack assembly ofFIG. 2; and

FIG. 13 is a cross-sectional side view of a portion of an accumulator ofthe BOP stack assembly of FIG. 2 having ultrasonic transducers.

DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS

One or more specific embodiments of the present invention will bedescribed below. These described embodiments are only exemplary of thepresent invention. Additionally, in an effort to provide a concisedescription of these exemplary embodiments, all features of an actualimplementation may not be described in the specification. It should beappreciated that in the development of any such actual implementation,as in any engineering or design project, numerousimplementation-specific decisions must be made to achieve thedevelopers' specific goals, such as compliance with system-related andbusiness-related constraints, which may vary from one implementation toanother. Moreover, it should be appreciated that such a developmenteffort might be complex and time consuming, but would nevertheless be aroutine undertaking of design, fabrication, and manufacture for those ofordinary skill having the benefit of this disclosure.

The present embodiments are generally directed to systems and methodsfor monitoring BOP equipment. More particularly, the present embodimentsare directed to systems and methods that utilize ultrasonic transducersto monitor a state (e.g., a position, a condition, or the like) of acomponent of a BOP stack assembly. For example, in some embodiments,ultrasonic transducers may be disposed on a body of a BOP (e.g., a ramBOP) of the BOP stack assembly. In some such embodiments, the ultrasonictransducers may be utilized to monitor a position of a moving componentof the BOP, such as a ram or a piston. In some embodiments, theultrasonic transducers may be disposed on a body of an accumulator ofthe BOP stack assembly and may be utilized to monitor a position of apiston of the accumulator. In certain embodiments, the ultrasonictransducers may include phased array ultrasonic transducers. In someembodiments, the phased array ultrasonic transducers may enable imagingof a component of the BOP, such as the ram, the piston, and/or a seal(e.g., a packer, an elastomer seal, a metal seal, a metal end cap seal,or the like) disposed on a contacting surface of the ram. The phasedarray ultrasonic transducers may be part of an imaging system. Incertain embodiments, the phased array ultrasonic transducers may enableimaging of a tubular string (e.g., drill string) disposed within a boreof the BOP. The phased array ultrasonic transducers may further enablevisualization and/or detection of a condition (e.g., wear ordeterioration) of the one or more seals. In certain embodiments, thesystems and methods may provide an output (e.g., a visual and/or anaudible output) indicative of the state of the component of the BOPand/or of the tubular string.

With the foregoing in mind, FIG. 1 is an embodiment of an offshoresystem 10. The offshore system 10 includes an offshore vessel orplatform 12 at a sea surface 14. A BOP stack assembly 16 is mounted to awellhead 18 at a sea floor 20. A tubular drilling riser 22 extends fromthe platform 12 to the BOP stack assembly 16. The riser 22 may returndrilling fluid or mud to the platform 12 during drilling operations.Downhole operations are carried out by a tubular string 24 (e.g., drillstring, production tubing string, or the like) that extends from theplatform 12, through the riser 22, through a bore 25 of the BOP stackassembly 16, and into a wellbore 26.

To facilitate discussion, the BOP stack assembly 16 and its componentsmay be described with reference to an axial axis or direction 30, alongitudinal axis or direction 32, and a lateral axis or direction 34.As shown, the BOP stack assembly 16 includes a BOP stack 38 havingmultiple BOPs 40 (e.g., ram BOPs) axially stacked (e.g., along the axialaxis 30) relative to one another. As discussed in more detail below,each BOP 40 includes a pair of longitudinally opposed rams andcorresponding actuators 42 that actuate and drive the rams toward andaway from one another along the longitudinal axis 32. Although four BOPs40 are shown, the BOP stack 38 may include any suitable number of BOPs(e.g., 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 or more). Additionally, the BOPstack 38 may include any of a variety of different types of rams. Forexample, in certain embodiments, the BOP stack 38 may include one BOP 40having opposed shear rams or blades configured to sever the tubularstring 24 and seal off the wellbore 26 from the riser 22 and one or moreBOPs 40 having opposed pipe rams configured to engage the tubular string24 and to seal the bore 25 (i.e., the annulus around the tubular string24 disposed within the bore 25). As discussed in more detail below,ultrasonic transducers 28 may be coupled to each of the BOPs 40 tofacilitate monitoring a state (e.g., a position, a condition, or thelike) of components (e.g., a ram, a piston, a seal) of the BOP 40 and/ora state of the tubular string 24. In some embodiments, the ultrasonictransducers 28 may be retrofitted to existing BOPs 40.

FIG. 2 is a perspective view of an embodiment of the BOP stack assembly16. As discussed above, the BOP stack 38 includes multiple BOPs 40axially stacked (e.g., along the axial axis 30) relative to one another.As shown, the BOP stack 38 also includes one or more hydraulicaccumulators 46. The hydraulic accumulators 46 may supply hydraulicpressure to the actuators 42 that are configured to drive the rams ofthe BOPs 40. As noted above, ultrasonic transducers 28 may be providedto facilitate monitoring a state of a component (e.g., a ram, a piston,a seal) of the BOP 40 and/or of the tubular string 24. The state mayinclude a position of a movable component, a condition, such as wear, ora combination thereof. Additionally or alternatively, in someembodiments, ultrasonic transducers 28 may be coupled to each of thehydraulic accumulators 46 to facilitate monitoring a state of movablecomponents (e.g., a piston) of the hydraulic accumulator 46.

FIG. 3 is a cross-sectional top view of a portion of one BOP 40 withopposed rams 50 in an open position 52. In the open position 52, eachram 50 is withdrawn from the bore 25, does not contact the tubularstring 24, and/or does not contact the corresponding opposed ram 50. Asshown, the BOP 40 includes a body 54 (e.g., housing) surrounding thebore 25. The body 54 is generally rectangular in the illustratedembodiment, although the body 54 may have any cross-sectional shape,including any polygonal shape or an annular shape. A bonnet assembly 58is mounted to the body 54 (e.g., via threaded fasteners). The bonnetassembly 58 may support the actuators 42, which each include a piston 60and a connecting rod 62. The actuators 42 may drive the opposed rams 50toward and away from one another along the longitudinal axis 32 andthrough the bore 25 to shear the tubular string 24 or to seal the bore25 (i.e., the annulus about the tubular string 24).

The ultrasonic transducers 28 may be coupled to an exterior surface 72of the body 54 of the BOP 40. In some embodiments, the ultrasonictransducers 28 may be arranged to form one or more pairs of ultrasonictransducers 70. In the illustrated embodiment, each pair of ultrasonictransducers 70 includes a first transducer 28 a on a first lateral side76 of the body 54 and a corresponding second transducer 28 b on a secondlateral side 80 of the body 54, opposite the first lateral side 76. Thefirst transducer 28 a and the second transducer 28 b of each pair ofultrasonic transducers 70 are longitudinally aligned with one another(e.g., along the longitudinal axis 32). In the illustrated embodiment,the first transducers 28 a of multiple pairs of ultrasonic transducers70 are coupled to one another and the second transducers 28 b ofmultiple pairs of ultrasonic transducers 70 are coupled to another,thereby forming opposing rows (e.g., laterally opposing rows) oftransducers 28 that extend longitudinally (e.g., along the longitudinalaxis 32) along the body 54 of the BOP 40. In some embodiments, multipleopposing rows of transducers 28 may extend longitudinally along the body54 of the BOP 40.

In some embodiments, the first transducer 28 a and the second transducer28 b may be discrete transducers each having one or more piezoelectricelements. In some embodiments, the first transducer 28 a and the secondtransducer 28 b may be configured to operate in a pitch catch mode inwhich an acoustic wave emitted by one transducer is detected by anothercorresponding transducer. For example, in some embodiments, the firsttransducer 28 a may be configured to operate as an emitter and thesecond transducer 28 b may be configured to operate as a detector. Inparticular, the first transducer 28 a may emit an acoustic wave in adirection approximately perpendicular to a direction of travel of theram 50 (e.g., perpendicular to the longitudinal axis 32) along a path 82toward the corresponding second transducer 28 b. The correspondingsecond transducer 28 b may detect the acoustic wave if the ram 50 doesnot block the path 82. Thus, detection of the acoustic wave at thesecond transducer 28 b and/or absence of detection of the acoustic waveat the second transducer 28 b may be indicative of a position (e.g.,along the longitudinal axis 32) of the rams 50.

For example, while the ram 50 is in the open position 52, at least oneor more of the second transducers 28 b may detect acoustic waves emittedby corresponding first transducers 28 a. As the ram 50 moves from theopen position 52 into the bore 25 as shown by arrow 84, the ram 50 mayblock detection of acoustic waves by a progressively greater number ofthe second transducers 28 b. Each of the second transducers 28 b may beconfigured to generate a signal in response to detection of acousticwaves, and the signal may be provided to a controller that is configuredto process the signal to determine a position of the rams 50.Additionally or alternatively, in some embodiments, the secondtransducers 28 b may be configured to emit acoustic waves, and eachfirst transducer 28 a may be configured to detect acoustic waves emittedby the corresponding second transducer 28 b.

Additionally or alternatively, in some embodiments, the first transducer28 a and/or the second transducer 28 b of each of the one or more pairsof ultrasonic transducers 70 may be configured to emit acoustic wavesand to receive reflected acoustic waves reflected from a surface 78 ofthe ram 50 or from a surface 79 of the connecting rod 62. For example,the first transducer 28 a and/or the second transducer 28 b may beexcited by respective drive signals to emit respective acoustic waves,and then the first transducer 28 a and/or the second transducer 28 b mayreceive respective reflected acoustic waves if the ram 50 is positionedbetween the first transducer 28 a and the corresponding secondtransducer 28 b. The first transducer 28 a and/or the second transducer28 b may generate signals in response to detection of the reflectedacoustic waves. As discussed below, a controller may be configured toprocess the signals generated by the first transducer 28 a and/or thesecond transducer 28 b to determine the position of the rams 50.

In the illustrated embodiment, eight pairs of ultrasonic transducers 70extend longitudinally on the exterior surface 72 of the body 54.Although eight pairs of ultrasonic transducers 70 are shown, anysuitable number of pairs of ultrasonic transducers 28 (e.g., 1, 2, 3, 4,5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23,24, 25 or more) may be provided. The number of pairs of ultrasonictransducers 70 and/or the spacing between each transducer 28 affects theaccuracy of the determination of the position of the rams 50. As shown,the one or more pairs of ultrasonic transducers 70 are spaced (e.g.,extend) longitudinally (e.g., along the longitudinal axis 32) across aportion of the bore 25 between respective contacting surfaces 77 (e.g.,a front edge) of the opposing rams 50 while the rams 50 are in the openposition 52 to enable detection of movement of the rams 50 toward thetubular string 24. However, in some embodiments, the one or more pairsof ultrasonic transducers 70 may extend longitudinally across anysuitable portion of the bore 25. In some embodiments, the one or morepairs of ultrasonic transducers 70 may extend across the entire bore 25(i.e., between longitudinal ends 79 of the bore 25).

Additionally or alternatively, as shown, ultrasonic transducers 28 maybe provided on an exterior surface 90 the bonnet 58 of the BOP 40 tofacilitate monitoring a position of the piston 60 of the actuator 42.The position of the piston 60 may be indicative of the position of theram 50 (e.g., indicative of whether the ram 50 is in the open position52, in a closed position, or a position therebetween). The ultrasonictransducers 28 may be arranged in one or more pairs of ultrasonictransducers 70 and may include any of the features discussed herein withrespect to the one or more pairs of ultrasonic transducers 70 utilizedto monitor the position of the rams 50.

FIG. 4 is a cross-sectional top view of a portion of one BOP 40 havingthe opposed rams 50 in a closed position 92. In the closed position 92,each ram 50 is advanced into the bore 25, contacts the tubular string24, and/or contacts a respective opposing ram 50. In the closed position92, the rams 50 may seal the bore 25 (i.e., the annulus about thetubular string 24) and/or may block a flow of fluid from the wellbore 26through the bore 25. As discussed above, detection of acoustic waves atthe first transducers 28 a and/or at the second transducers 28 b may beindicative of a position (e.g., along the longitudinal axis 32) of theram 50. For example, while the rams 50 are in the closed position 92,the ram 50 may block transmission of acoustic waves between the firsttransducer 28 a and the corresponding second transducer 28 b of each ofthe one or more ultrasonic transducer pairs 70. Thus, in someembodiments, while the rams 50 are in the closed position 92, none ofthe second transducers 28 b detect acoustic waves emitted bycorresponding first transducers 28 a. Furthermore, in some embodiments,while the rams 50 are in the closed position 92, the first transducers28 a and/or the second transducers 28 b may detect reflected acousticwaves. As discussed below, a controller may be configured to process thesignals generated by the first transducer 28 a and/or the secondtransducer 28 b to determine the position of the rams 50.

In certain embodiments, the ultrasonic transducers 28 may be phasedarray ultrasonic transducers. Accordingly, FIG. 5 is a cross-sectionaltop view of a portion of the BOP 40 having phased array ultrasonictransducers 100. In some embodiments, the phased array ultrasonictransducers 100 may be coupled to the exterior surface 72 of the body 54of the BOP 40. In some embodiments, the phased array ultrasonictransducers 100 may be arranged to form one or more pairs of phasedarray ultrasonic transducers 102. In the illustrated embodiment, eachpair of phased array ultrasonic transducers 102 includes a firsttransducer 100 a on the first lateral side 76 of the body 54 and thecorresponding second transducer 100 b on the second lateral side 80 ofthe body 54, opposite the first lateral side 76. The first transducer100 a and the second transducer 100 b of each pair of phased arrayultrasonic transducers 102 are longitudinally aligned with one another(e.g., along the longitudinal axis 32). In the illustrated embodiment,the first transducers 100 a of multiple pairs of phased array ultrasonictransducers 102 are coupled to one another and the second transducers100 b of multiple pairs of phased array ultrasonic transducers 102 arecoupled to another, thereby forming opposing rows (e.g., laterallyopposing rows) of transducers 100 that extend longitudinally along thebody 54 of the BOP 40.

Each phased array ultrasonic transducer 100 a, 100 b includes multiplepiezoelectric elements. Furthermore, each phased array ultrasonictransducer 100 a, 100 b is configured to electronically steer (e.g.,guide or direct) a beam of acoustic waves through an angle 108. Theangle 108 may be any suitable angle for monitoring a portion of the BOP40. For example, the angle 108 may be greater than approximately 20, 40,60, 80, 100, 120, 140, or 160 degrees.

In some embodiments, the first transducer 100 a and/or the secondtransducer 100 b may be configured to operate in a pulse echo mode inwhich an acoustic wave emitted by one transducer is reflected anddetected by the same transducer. In such cases, the first transducer 100a and/or the second transducer 100 b may be configured to emit anacoustic wave and to detect the respective reflected acoustic wave(e.g., reflected by the surface 78 of the ram 50 or by the surface 79 ofthe connecting rod 62). Detection of the reflected acoustic wave at thefirst and/or second transducers 100 a, 100 b and/or absence of detectionof the reflected acoustic wave at the first and/or second transducers100 a, 100 b may be indicative of a position (e.g., along thelongitudinal axis 32) of the ram 50. For example, detection of therespective reflected acoustic wave at the first and/or the secondtransducer 100 a, 100 b may indicate that the ram 50 is positionedbetween the first and the second transducer 100 a, 100 b.

As discussed in more detail below, the reflected acoustic waves receivedby the first transducer 100 a and/or by the second transducer 100 b maybe converted into electrical signals and provided to a controllercoupled to the BOP 40. In some embodiments, the controller may beconfigured to process the signals to determine a position of the rams50. For example, the controller may be configured to generate an image(e.g., an outline image) of the rams 50 based on the signals and todetermine the position of the rams 50 within the bore 25 based at leastin part on the image (e.g., by aligning the image of the rams 50 withinthe monitored portion of the bore 25). As discussed in more detailbelow, in some embodiments, the controller may be configured to generateand/or output the image of the rams 50. For example, the controller mayoutput the image of the rams 50 on a display to enable an operator tovisualize the position of the rams 50. In certain embodiments, thedisplayed image may be updated as the rams 50 move to enable theoperator to view the movement of the rams 50 within the bore 25.

In FIG. 5, each ram 50 is in the open position 52. While the rams 50 arein the open position 52, at least one or more of the first and/or secondtransducers 100 a, 100 b may not detect reflected acoustic waves becausethe rams 50 are not advanced through the bore 25. As the rams 50 movefrom the open position 52 into the bore 25 as shown by arrow 110, therams 50 may reflect the acoustic waves toward a progressively greaternumber of the first and second transducers 100 a, 100 b. For example,when the rams 50 are in the closed position 92 discussed above, the rams50 may reflect or block the acoustic waves emitted by all of the firstand second transducers 100 a, 100 b.

In the illustrated embodiment, eight pairs of phased array ultrasonictransducers 100 are spaced (e.g., extend) longitudinally (e.g., alongthe longitudinal axis 32) on the exterior surface 72 of the body 54.Although eight pairs of ultrasonic transducers 100 are shown, anysuitable number of pairs of phased array ultrasonic transducers 100(e.g., 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, or more) may be provided.The number of pairs of phased array ultrasonic transducers 100 and/orthe spacing between the transducers 100 affects the accuracy of thedetermination of the position of the rams 50 and/or affects completenessof an image generated based on signals received from the phased arrayultrasonic transducers 100. As shown, the one or more pairs ofultrasonic transducers 102 extend longitudinally across a length of thebore 25 (i.e., from one side of the bore 25 to the other side of thebore 25). However, in some embodiments, the one or more pairs ofultrasonic transducers 102 may extend longitudinally along any suitableportion of the length of the bore 25. For example, the one or more pairsof ultrasonic transducers 102 may only be provided at longitudinalpositions along the body 54 of the BOP 40 that lie between respectivecontacting surfaces 77 (e.g., a front edge) of the opposing rams 50while the rams 50 are in the open position 52 to enable detection ofmovement of the rams 50 toward the tubular string 24.

Additionally, although FIG. 5 shows one or more pairs of phased arrayultrasonic transducers 102 having the first transducer 100 a and thesecond transducer 100 b, it should be understood that in someembodiments, one or more phased array ultrasonic transducers 100 may beprovided on only one lateral side of the body 54 of the BOP 40. Whilepairs 102 of laterally opposed phased array ultrasonic transducers 100may provide redundancy in measurement and/or a more complete image ofthe rams 50 or other components of the BOP 40, one or more phased arrayultrasonic transducers 100 on one lateral side (e.g., the first lateralside 76 or the second lateral side 80) may provide sufficientinformation to enable the controller to generate an image, determine acondition (e.g., a wear condition) of a component of the BOP 40, and/orto determine the position of the ram 50, for example.

FIG. 6 is a cross-sectional side view of a portion of the BOP 40 havingmultiple phased array ultrasonic transducers 100. As shown, the multiplephased array ultrasonic transducers 100 may be coupled to one anotherand arranged in one or more columns 114 each extending axially (e.g.,along the axial axis 30) of the BOP 40. Thus, the multiple phased arrayultrasonic transducers 100 may extend along the axial axis 34 of thebody 54 that is perpendicular to the direction of movement 110 of theram 50. In some embodiments, the multiple phased array ultrasonictransducers 100 may be arranged in multiple columns 114 to form a grid113 of phased array ultrasonic transducers 100 extending axially andlongitudinally (e.g., along the longitudinal axis 32) to enablemonitoring of a larger surface area of the ram 50, a seal 104 on thecontacting surface 77 of the ram 50, and/or of the tubular string 24,for example. The grid 113 may include 2 to 50 phased array ultrasonictransducers 100 extending axially and 2 to 50 phased array ultrasonictransducers 100 extending longitudinally. In some embodiments, the grid113 of multiple phased array ultrasonic transducers 100 may extend anaxial height 116 greater than an axial height 118 of the rams 50 and/ormay extend a longitudinal length 120 greater than a longitudinal length122 of the tubular string 24. In some embodiments, as shown, one or morerows 124 of the multiple phased array ultrasonic transducers 100 mayextend longitudinally (e.g., along the longitudinal axis 32) between therams 50 and may facilitate monitoring the position of the rams 50 in themanner discussed above with respect to FIG. 5.

In some embodiments, similar to the embodiment discussed above withrespect to FIG. 5, the multiple phased array ultrasonic transducers 100may be arranged in multiple pairs positioned on opposite lateral sidesof the body 54 of the BOP 40 to enable monitoring the components (e.g.,the ram 50, the seal 104, and/or the tubular string 24) from bothlateral sides of the body 54. Additionally, the phased array ultrasonictransducers 100 may be configured to operate in a pulse-echo mode andmay include any of the features discussed above with respect to FIG. 5.

As discussed in more detail below, the reflected acoustic waves receivedby the phased array ultrasonic transducers 100 may be converted intoelectrical signals and provided to a controller (e.g., an electroniccontroller with a processor and a memory) coupled to the BOP 40. In someembodiments, the controller may be configured to process the signals todetermine a position of the ram 50. In some embodiments, the controllermay be configured to process the signals to determine a condition of acomponent of the BOP 40 and/or a condition of the tubular string 24. Forexample, the controller may be configured to determine whether the seal104 is worn or deteriorated (e.g., a wear condition) based on thesignals and/or whether the tubular string 24 is severed. In someembodiments, the controller may be configured to generate a visualrepresentation (e.g., an image) of a component of the BOP 40 and/or ofthe tubular string 24. For example, the controller may be configured togenerate and/or output an image (e.g., a two dimensional image) of theram 50, the seal 104, and/or the tubular string 24. Thus, theembodiments may enable visualization of the ram 50, the seal 104, thebore 25, movement of the ram 50 within the bore 25, the tubular string24, and/or a process of severing of the tubular string 24. In certainembodiments, one or more columns 114 of phased array transducers 100 maybe provided to facilitate monitoring and/or imaging the ram 50, the seal104, and/or the tubular string 24 and discrete ultrasonic transducers 28may be arranged in one or more pairs 70 to facilitate monitoring aposition of the rams 50 as discussed above with respect to FIGS. 2 and3.

FIG. 7 is a top view of a portion of the BOP 40 having slots 130 (e.g.,openings or cavities) configured to support the ultrasonic transducers28. One slot 130 may be positioned on a first lateral side 132 of thebore 25 and another slot 130 may be positioned on a second lateral side134 of the bore 25, opposite the first side 132. Each of the one or moreslots 130 extends along the longitudinal axis 32. Additionally, each ofthe slots 130 may be configured to receive one or more ultrasonictransducers 28 via an opening 136 formed in a longitudinally-facingsurface 138 (e.g., relative to the longitudinal axis 32) of the body 54.For example, an array (e.g., a linear array, a row, or a cartridge) ofmultiple first transducers 28 a that are coupled to one another may beinserted through the opening 136 and into one of the slots 130. Theslots 130 may facilitate proper positioning of the ultrasonictransducers 28 relative to one another and/or relative to the rams 50.Additionally, the slots 130 may enable efficient removal of theultrasonic transducers 28 for inspection, repair, and/or replacement. Insome embodiments, one or more slots 140 may extend along the axial axis30 to receive and to support the one or more columns 114 and/or thegrids 113 of the multiple phased array ultrasonic transducers 100discussed above with respect to FIG. 6.

FIG. 8 is a side view of the portion of the BOP 40 having the slots 130configured to support the ultrasonic transducers 28. As shown, the slots130 are axially aligned with the rams 50 to facilitate monitoring aposition of the rams 50, although the slots 130 may be positioned in anysuitable axial location to facilitate monitoring the various componentsof the BOP 40. In some embodiments, one or more slots 140 may extendalong the axial axis 30 to receive and to support the one or morecolumns 114 and/or the grids 113 of the multiple phased array ultrasonictransducers 100 discussed above with respect to FIG. 6.

FIG. 9 is a schematic diagram of an embodiment of a BOP system 148configured to monitor a position of a movable component (e.g., the rams50, the piston 60) of the BOP 40. Additionally or alternatively, thesystem 148 may be configured to monitor a position of a piston of thehydraulic accumulator 46. Additionally or alternatively, the system 148may be configured to monitor a condition (e.g., a wear condition,cracks, breakage, erosion, corrosion, or the like) of a component of theBOP 40, such as a condition of the seal 104. Additionally oralternatively, the system 148 may be configured to monitor a conditionof the tubular string 24. As shown, each BOP 40 includes the actuators42 configured to actuate (e.g., drive translation of) a respective ram50. The system 148 also includes a controller 150 that may be coupled tovarious components of the BOP 40. In certain embodiments, the controller150 is an electronic controller having electrical circuitry configuredto process signals from and/or to provide control signals to certaincomponents of the system 148.

In the illustrated embodiment, the controller 150 includes a processor,such as the illustrated microprocessor 152, and the memory device 154.The controller 150 may also include one or more storage devices and/orother suitable components. The processor 152 may be used to executesoftware, such as software for controlling the system 148. Moreover, theprocessor 152 may include multiple microprocessors, one or more“general-purpose” microprocessors, one or more special-purposemicroprocessors, and/or one or more application specific integratedcircuits (ASICS), or some combination thereof. For example, theprocessor 152 may include one or more reduced instruction set (RISC) orcomplex instruction set (CISC) processors.

The memory device 154 may include a volatile memory, such as randomaccess memory (RAM), and/or a nonvolatile memory, such as ROM. Thememory device 154 may store a variety of information and may be used forvarious purposes. For example, the memory device 154 may storeprocessor-executable instructions (e.g., firmware or software) for theprocessor 152 to execute, such as instructions for controlling thesystem 148. The storage device(s) (e.g., nonvolatile storage) mayinclude read-only memory (ROM), flash memory, a hard drive, or any othersuitable optical, magnetic, or solid-state storage medium, or acombination thereof. The storage device(s) may store data (e.g.,position data, condition data, image data, thresholds, or the like),instructions (e.g., software or firmware for controlling the system 148,or the like), and any other suitable data.

In certain embodiments, the controller 150 is configured to control eachactuator 42 to adjust a position of the respective ram 50. Thecontroller 150 may be configured to control each actuator 42automatically based on well conditions (e.g., well pressure) and/orbased on an operator input received via a user input 156 (e.g., aswitch, button, or the like), for example. The user input 156 may bepart of a user interface that includes a display 158. In someembodiments, the user input 156 may be a virtual user input (e.g.,displayed on a touch screen of the display 158) configured to receivethe operator input.

In certain embodiments, the controller 150 is configured to provide asignal to drive one or more transducers 28 to emit an acoustic wave. Insome embodiments, the controller 150 may provide the drive signal inresponse to an operator input received via the user input 156 and/or inresponse to initiation of movement of the rams 50. In some embodiments,the controller 150 may provide the drive signal continuously orperiodically during movement of the rams 50 to facilitate monitoring ofthe movement of the rams 50. In some embodiments, the controller 150 mayprovide the drive signal continuously or periodically while the rams 50are in the closed position 92 to facilitate monitoring the contactbetween the rams 50 and the tubular string 24.

In certain embodiments, the controller 150 may provide a drive signal todrive at least one transducer 28 (e.g., the first transducer 28 a of onepair of transducers 70) to emit an acoustic wave. As noted above, theacoustic wave may be received by a corresponding transducer 28 (e.g.,the second transducer 28 b) disposed on an opposite side of the bore 25or by the same transducer (e.g., the first transducer 28 a) afterreflection from the surface 78 of the ram 50. The transducers 28 maygenerate a signal in response to the detected acoustic wave that isindicative of a position of the ram 50. The controller 150 may beconfigured to receive and to process signals generated by thetransducers 28 of the one or more pairs of ultrasonic transducers 70. Insome embodiments, the controller 150 may be configured to determine aposition of the rams 50 based on the signals, as discussed above.

Additionally or alternatively, the controller 150 may be configured toprocess the signals received from the transducers 28 to determine acondition (e.g., a wear condition, cracks, breakage, erosion, corrosion,velocity, acceleration, or the like) of components of the BOP 40. Forexample, in some embodiments, the controller 150 may be configured tomonitor a velocity and/or an acceleration of the ram 50 based on signalintegration of the signals received from the transducers 28 (e.g., basedon a change in position over time), to compare the velocity and/or theacceleration to thresholds (e.g., predetermined thresholds stored in amemory device 154) related to an expected velocity and/or accelerationof the ram 50, and to determine a condition of components of the BOPsystem 148 (e.g., to determine whether components of the BOP system 148are operating as expected, are damaged, or the like) based on thecomparison. For example, if the velocity is below the predeterminedthreshold, the controller 150 may determine that mechanical componentsof the BOP 40 may not be operating correctly and the controller 150 mayprovide an indication (e.g., a displayed indication of the display 158or an audible indication) that the velocity of the ram 50 is below thepredetermined threshold and/or that the BOP 40 is not operatingcorrectly. In some such embodiments, the controller 150 may provideinstructions (e.g., displayed or audible instructions) to inspect,repair, and/or replace certain components of the BOP 40, for example.

As discussed above, the transducers 28 may include phased arrayultrasonic transducers 100. In some such embodiments, the system 148 maybe adapted to generate an image of various components of the BOP 40(e.g., the ram 50, the piston 60, and/or the seal 104). The phased arrayultrasonic transducers 100 may be configured to operate in a pulse-echomode. Multiple phased array ultrasonic transducers 100 may extendlongitudinally and/or axially along the body 54 of the BOP 40 and eachphased array ultrasonic transducer 100 may be configured to steer itsacoustic beam through the angle 108. Each phased array ultrasonictransducer 100 may detect a reflected acoustic wave (e.g., reflectedfrom the surface 78 of the ram 50) and generate a signal based on thedetected reflected acoustic wave.

In some embodiments, the controller 150 may be configured to process thesignals to determine a position of the rams 50. For example, thecontroller 150 may be configured to generate an image (e.g., an outlineimage) of the rams 50 based on the signals received from the phasedarray ultrasonic transducers 100 and to determine the position of therams 50 within the bore 25 based at least in part on the image (e.g., byaligning the image of the rams 50 within the monitored portion of thebore 25). In particular, the controller 150 may be configured togenerate the image of the rams 50 or of any components disclosed hereinvia any suitable image processing technique. Once the image is formed,the controller 150 may apply techniques such as averaging, stacking,contrast enhancement, and/or histogram manipulation to facilitateanalysis of the image. The controller 150 may then analyze the image viaedge detection, pattern matching, or other techniques to identifyelements of interest in the image, such as the ram 50 or the piston 60,and the position of the element of interest within the bore 25, forexample. In some embodiments, the controller 150 may be configured togenerate and/or output the position of the rams 50 and/or the image ofthe rams 50. For example, the controller may output the image of therams 50 on the display 158 to enable an operator to visualize theposition of the rams 50.

In some embodiments, the controller 150 may be configured to generatemultiple images of the ram 50 as the ram 50 moves between the openposition 52 and the closed position 92. In some embodiments, thecontroller 150 may generate an image at a rate of approximately oneframe per second, or any other suitable rate (e.g., less than 5, 4, 3,2, 1, 0.5 frames per second). The controller 150 may output the imageand update the image over time, thereby enabling output of a video ofthe movement of the ram 50 in substantially real-time. The image mayenable the operator to visualize the position of the ram 50 within thebore 25 and/or movement of the ram 50 within the bore 50. The userinterface may enable the operator to interact with the image (e.g., viathe user input 156 or via a touch screen of the display 158), therebyenabling the operator to select, replay, focus, or otherwise manipulatethe image. Thus, the controller 150 may be part of a real timemonitoring system configured to generate images and/or enablevisualization of real-time movement and objects (e.g., the rams 50, theseals 104, the tubular string 24, or the like) within the BOP system148.

In some embodiments, the controller 150 may be configured to determine acondition (e.g., a wear condition, cracks, breakage, erosion, corrosion,velocity, acceleration, or the like) of components of the BOP 40 (e.g.the seal 104 or mechanical components) based on the signals. Forexample, as discussed above, the controller 150 may be configured tomonitor a velocity and/or an acceleration of the ram 50 based on thesignals received from the phased array ultrasonic transducers 100, tocompare the velocity and/or the acceleration to thresholds (e.g.,predetermined thresholds stored in a memory device 154) related to anexpected velocity and/or acceleration of the ram 50, and to determine acondition of components of the BOP system 148 (e.g., to determinewhether components of the BOP system 148 are operating as expected, aredamaged, or the like) based on the comparison. In some embodiments, thecontroller 150 may be configured to monitor the velocity and/or theacceleration of the ram 50 based on signal integration of signalsreceived from individual ultrasonic transducers 28 (e.g., phased arrayultrasonic transducers 100) or based on images generated via imageprocessing techniques using the signals received from the phased arrayultrasonic transducers 100.

Additionally or alternatively, acoustic waves may be reflected by one ormore seals 104 on the contacting surface 77 of the ram 50. The signalgenerated by the phased array ultrasonic transducers 100 in response todetection of these reflected acoustic waves may enable the controller150 to determine a condition of the seal 104. For example, thecontroller 150 may be configured to determine a thickness of the sealbased on the signal, to compare the thickness to thresholds (e.g.,predetermined thresholds stored in a memory device 154) related to anacceptable thickness of the seal 104, and to determine a condition ofthe seal 104 based on the comparison. In some embodiments, thecontroller 150 may be configured to detect anomalies or defects of theseal 104 (e.g., in a surface of the seal 104) via any suitable imageprocessing and/or analysis techniques. For example, the controller 150may analyze the image via pattern matching (e.g., comparing the image toone or more reference images of damaged and/or intact seals 104 storedin the memory device 154) to detect defects and/or to classify thedefects (e.g., classify the type of defect, such as a tear, and/or theseverity of the defect) based on defect characteristics (e.g., size,depth, geometry, or the like). In some embodiments, the controller 150may provide an output indicative of the condition of the seal 104. Forexample, the controller 150 may provide an output indicative of themeasured thickness of the seal 104 compared to an initial thicknessand/or compared to the acceptable thickness (e.g., a percentage). Insome embodiments, the controller 150 may output instructions (e.g.,displayed or audible instructions) to inspect, repair, and/or replacethe seal 104, for example. In certain embodiments, the controller 150may generate and output an image of the seal 104, thereby enabling theoperator to visualize the condition of the seal 104. For example, wearand/or imperfections in the seal 104 may be visible and/or highlightedin the image. Although the detection of defects is discussed in thecontext of the seal 104 to facilitate discussion, it should beunderstood that the phased array ultrasonic transducers 100 and thesetechniques for detecting defects may be applied to any component withinor associated with the BOP system 148, such as the rams 50, the tubularstring 24, or the like.

Additionally or alternatively, the system 148 may be adapted to generatean image of the tubular string 24 extending through the bore 25 of theBOP 40 using the phased array ultrasonic transducers 100. As notedabove, the phased array ultrasonic transducers 100 may be configured tooperate in a pulse-echo mode, and the controller 150 may be configuredto electronically steer (e.g., guide or sweep) each acoustic beamthrough the angle 108. Each phased array ultrasonic transducer 100 maydetect a reflected acoustic wave (i.e., reflected from the tubularstring 24) and generate a signal based on the detected reflectedacoustic wave. The controller 150 may receive the signal and maygenerate an image (e.g., an outline image) of the tubular string 24. Insome embodiments, the controller 150 may be configured to generatemultiple images of the tubular string 24 and/or the ram 50 as the ram 50severs the tubular string 24. In some embodiments, the controller 150may generate an image at a rate of approximately one frame per second,or any other suitable rate (e.g., less than 5, 4, 3, 2, 1, 0.5 framesper second). The controller 150 may output the image and update theimage over time, thereby enabling output of a video of the movement ofthe ram 50 and/or severing of the tubular string 24 in substantiallyreal-time. The image may enable the operator to visualize a state (e.g.,a condition) of the tubular string 24, including whether the tubularstring 24 was severed by the ram 50. In some embodiments, the controller150 may be configured to overlay the image (e.g., the current image)over a baseline image (e.g., intact tubular string 24 or the tubularstring 24 prior to operation of the offshore system 10) on the display158, or otherwise display both the current image and the baseline image(e.g., side-by-side) to enable the operator to visualize changes. Inaddition to the examples provided above, the system 148 of FIG. 9 may beadapted to perform any of the monitoring methods or techniques disclosedherein. For example, the system 148 may be adapted to monitor a positionof a piston of the hydraulic accumulator 46 discussed below with respectto FIG. 13.

FIGS. 10, 11, and 12 are flow charts illustrating various methods formonitoring components (e.g., the ram 50, the seal 104, and/or the piston60) of the BOP stack assembly 38 and/or the tubular string 24, inaccordance with the present disclosure. The methods include varioussteps represented by blocks. It should be noted any of the methodsprovided herein, may be performed as an automated procedure by a system,such as system 148. Although the flow charts illustrate the steps in acertain sequence, it should be understood that the steps may beperformed in any suitable order and certain steps may be carried outsimultaneously, where appropriate. Further, certain steps or portions ofthe methods may be performed by separate devices. For example, a firstportion of the method may be performed by the processor 152, while asecond portion of the method may be performed by a separate processingdevice. As noted above, the methods for monitoring components of the BOPstack assembly 38 and/or the tubular string 24 may be initiatedautomatically (e.g., in response to initiation of movement of the rams50) or in response to operator input (e.g., via user input 156).

FIG. 10 is a flow diagram of an embodiment of a method 200 formonitoring a position of a movable component (e.g., the ram 50 or thepiston 60) of the BOP 40. The method 200 may be adapted to monitor aposition of the piston of the hydraulic accumulator 46 discussed belowwith respect to FIG. 13. As shown, the method 200 may begin with thecontroller 150 providing a drive signal to cause one transducer (e.g.,the first transducer 28 a) to emit an acoustic wave in step 202. Asdiscussed above with respect to FIGS. 3 and 4, the transducers 28 may bediscrete transducers arranged in one or more pairs of ultrasonictransducers 70 and may be operated in a pitch-catch mode. In such cases,the first transducer 28 a and the second transducer 28 b of each pair ofultrasonic transducers 70 are disposed on opposite lateral sides of thebore 25 of the BOP 40. In step 204, the controller 150 may determinewhether the acoustic wave is received at the corresponding secondtransducer 28 b.

If the acoustic wave is received at the corresponding second transducer28 b, the controller 150 may determine that the movable component is notpositioned between the first and second transducers 28 a, 28 b in step206. However, if the acoustic wave is not received at the correspondingsecond transducer 28 b, the controller 150 may determine that themovable component is positioned between the first and second transducers28 a, 28 b in step 208. The number of transducers 28 and/or the spacingbetween the transducers 28 affects the accuracy of the positiondetermination (e.g., more transducers 28 and/or closer spacing providesgreater accuracy). In some embodiments, the controller 150 may providean output indicative of the position of the movable component in step210. For example, the controller 150 may provide a displayed output onthe display 158 indicating that the movable component is in the openposition 52, the closed position 92, or a position therebetween.

As noted above, in some embodiments, the transducers 28 may be phasedarray ultrasonic transducers 100 that are configured to operate in apulse-echo mode. In such embodiments, the controller 150 may beconfigured to determine the position of the movable component based onwhether a reflected acoustic wave (e.g., reflected by the surface 78 ofthe ram 50) is received at the phased array ultrasonic transducer 100.Thus, the method 200 may be adapted to monitor the position of themovable component based on detection of the reflected acoustic waveusing phased array ultrasonic transducers 100. In some such embodiments,the displayed output may include an image of the movable component. Insome embodiments, the displayed output may include a video depictingmovement of the movable component over time.

FIG. 11 is a flow diagram of an embodiment of a method 220 formonitoring a condition (e.g., a wear condition, cracks, breakage,erosion, or the like) of the seal 104 of the BOP 40. The method 220 maybe carried out by the system 148 having multiple phased array ultrasonictransducers 100. As discussed above with respect to FIGS. 5 and 6, thephased array ultrasonic transducers 100 may be configured to operate ina pulse-echo mode. In step 222, the controller 150 may provide a drivesignal to cause one phased array ultrasonic transducer 100 to emit anacoustic wave. In step 224, the controller 150 may receive a signalgenerated by the phased array ultrasonic transducer 100 in response tothe reflected acoustic wave (e.g., reflected from a surface of the seal104).

In step 226, the controller 150 may process the signal to determine acondition of the seal 104. For example, the controller 150 may beconfigured to determine a thickness of the seal based on the signal, tocompare the thickness to predetermined thresholds (e.g., stored in thememory device 154) related to an acceptable thickness of the seal 104,and to determine a condition of the seal 104 based on the comparison. Insome embodiments, the controller 150 may generate an image of the seal104 and compare the image to a stored image of the seal 104 (e.g.,stored in the memory device 154), which may enable identification ofimperfections in the seal 104.

In step 228, the controller 150 may provide an output indicative of thecondition of the seal 104. For example, the controller 150 may providean output indicative of the measured thickness of the seal 104 comparedto an initial thickness and/or compared to the acceptable thickness(e.g., a percentage). In some embodiments, the controller 150 may outputinstructions (e.g., displayed or audible instructions) to inspect,repair, and/or replace the seal 104, for example. In certainembodiments, the controller 150 may generate and output an image of theseal 104, thereby enabling the operator to visualize the condition ofthe seal 104. For example, wear and/or imperfections in the seal 104 maybe visible in the image. It should be understood that the method 220 maybe adapted to determine the condition of various other components of theBOP stack assembly 38, such as the condition of the ram 50, the piston60, or the like.

FIG. 12 is a flow diagram of an embodiment of a method 240 formonitoring the tubular string 24 extending through the bore 25 of theBOP 40. The method 240 may be carried out by the system 148 havingmultiple phased array ultrasonic transducers 100. As discussed abovewith respect to FIGS. 5 and 6, the phased array ultrasonic transducers100 may be configured to operate in a pulse-echo mode. In step 242, thecontroller 150 may provide a drive signal to cause one phased arrayultrasonic transducer 100 to emit an acoustic wave. In step 244, thecontroller 150 may receive a signal generated by the phased arrayultrasonic transducer 100 in response to the reflected acoustic wave(e.g., reflected from a surface of the tubular string 24).

In step 246, the controller 150 may process the signal to generate animage of the tubular string 24. In step 248, the controller 150 mayprovide the image of the tubular string 24 on the display 158, therebyenabling the operator to visualize the tubular string 24. In someembodiments, the steps of method 240 may be repeated over time such thatthe controller 150 generates multiple images of the tubular string 24and/or the ram 50 as the ram 50 severs the tubular string 24. In someembodiments, the controller 150 may generate an image at a rate ofapproximately one frame per second, or any other suitable rate (e.g.,less than 5, 4, 3, 2, 1, 0.5 frames per second). In some such cases, thecontroller 150 may output the image and update the image over time,thereby enabling output of a video of the movement of the ram 50 and/orsevering of the tubular string 24 in substantially real-time. The imagemay enable the operator to visualize a state (e.g., a condition, a wearcondition, cracks, breakage, erosion, corrosion, or the like) of thetubular string 24, including whether the tubular string 24 was severedby the ram 50.

It should be understood that the steps of the method 240 may be adaptedto enable imaging of the tubular string 24 and/or the relative positionof the rams 50 (e.g., pipe rams or variable bore rams) to one anotherand to the tubular string 24 during sealing of the annulus about thetubular string 24. Such techniques may enable monitoring and/orvisualization of a distance between the rams 50 in order to determine ifthe rams 50 adequately contact one another about the tubular string 24when the rams 50 are in the closed position 92.

FIG. 13 is a cross-sectional side view of a portion of the hydraulicaccumulator 46 of the BOP stack assembly 38. The hydraulic accumulator46 may be described with reference to an axial axis or direction 250, alongitudinal axis or direction 252, and a lateral axis or direction 254.As shown, ultrasonic transducers 28 are coupled to opposite lateralsides of an exterior surface 260 of a body 262 of the hydraulicaccumulator 46 to facilitate monitoring a position of a piston 264. Theultrasonic transducers 28 may include any features discussed above. Forexample, the ultrasonic transducers 28 may be arranged to form one ormore pairs of ultrasonic transducers 70. Furthermore, in someembodiments, the first transducer 28 a and the second transducer 28 bmay be discrete transducers each having one or more piezoelectricelements.

In some embodiments, the first transducer 28 a and the second transducer28 b may be configured to operate in a pitch catch mode in which anacoustic wave emitted by one transducer is detected by anothercorresponding transducer. For example, the first transducer 28 a mayemit an acoustic wave in a direction approximately perpendicular to adirection of travel of the piston 264 (e.g., perpendicular to the axialaxis 250) along a path 266 toward the corresponding second transducer 28b. The corresponding second transducer 28 b may detect the acoustic waveif the piston 264 does not block the path 266. Thus, detection of theacoustic wave at the second transducer 28 b and/or absence of detectionof the acoustic wave at the second transducer 28 b may be indicative ofa position (e.g., along the axial axis 250) of the piston 264. In someembodiments, the transducers 28 may be phased array ultrasonictransducers 100 configured to operate in a pulse-echo mode and todetermine the position of the piston 264 based at least in part on animage of the piston 264, in the manner discussed above with respect toFIG. 5.

While the invention may be susceptible to various modifications andalternative forms, specific embodiments have been shown by way ofexample in the drawings and have been described in detail herein.However, it should be understood that the invention is not intended tobe limited to the particular forms disclosed. Rather, the invention isto cover all modifications, equivalents, and alternatives falling withinthe spirit and scope of the invention as defined by the followingappended claims.

The invention claimed is:
 1. A monitoring system for a blowout preventer(BOP) stack assembly, comprising: one or more pairs of ultrasonictransducers coupled to a body that is configured to support a movablecomponent of the BOP stack assembly, wherein each pair of ultrasonictransducers comprises a first ultrasonic transducer disposed on a firstside of the body and a second ultrasonic transducer disposed on a secondside of the body, opposite the first side; and a controller configuredto receive a first signal indicative of a position of the movablecomponent from the one or more pairs of ultrasonic transducers, todetermine the position of the movable component based on the firstsignal, and to provide a first output indicative of the position of themovable component; wherein at least one of the one or more pairs ofultrasonic transducers is configured to operate in a pitch catch mode inwhich the first ultrasonic transducer is configured to emit an acousticwave and the second ultrasonic transducer is configured to receive theacoustic wave.
 2. The system of claim 1, wherein each of the one or morepairs of ultrasonic transducers is configured to operate in a pitchcatch mode in which the first ultrasonic transducer is configured toemit an acoustic wave and the second ultrasonic transducer is configuredto receive the acoustic wave.
 3. The system of claim 1, wherein the oneor more pairs of ultrasonic transducers comprise phased arraytransducers.
 4. The system of claim 1, wherein the movable componentcomprises a ram of a BOP of the BOP stack assembly.
 5. The system ofclaim 1, wherein the movable component comprises a piston of an actuatorthat is configured to drive a ram of a BOP of the BOP stack assembly. 6.The system of claim 1, wherein the movable component comprises a pistonof an accumulator of the BOP stack assembly.
 7. The system of claim 1,wherein the controller is configured to generate an image of the movablecomponent in real-time based on the first signal, and the first outputcomprises a displayed image of the movable component.
 8. The system ofclaim 1, wherein the first output comprises a video depicting movementof the movable component.
 9. The system of claim 1, wherein the one ormore pairs of ultrasonic transducers are configured to generate a secondsignal indicative of a condition of an element of the BOP stackassembly, and the controller is configured to receive the second signal,to determine the condition of the element based on the second signal,and to provide a second output indicative of the condition of theelement.
 10. The system of claim 9, wherein the element is a sealdisposed on a surface of the movable component and the second outputcomprises a displayed image of the seal.
 11. The system of claim 1,wherein the one or more pairs of ultrasonic transducers are configuredto generate a second signal indicative of a condition of a tubularstring extending through a bore of the body, and the controller isconfigured to receive the second signal, to determine the condition ofthe tubular string based on the second signal, and to provide adisplayed image indicative of the condition of the tubular string. 12.The system of claim 1, wherein the controller is configured to determinea velocity or an acceleration of the movable component based on thefirst signal.
 13. A blowout preventer (BOP) system, comprising: a bodyconfigured to support a movable component of a BOP stack assembly; andone or more pairs of ultrasonic transducers coupled to the body, whereineach pair of ultrasonic transducers comprises a first ultrasonictransducer disposed on a first side of the body and a second ultrasonictransducer disposed on a second side of the body, opposite the firstside, and wherein the one or more pairs of ultrasonic transducers areconfigured to generate a signal indicative of a position of the movablecomponent, and wherein at least one of the one or more pairs ofultrasonic transducers is configured to operate in a pitch catch mode inwhich the first ultrasonic transducer is configured to emit an acousticwave and the second ultrasonic transducer is configured to receive theacoustic wave.
 14. The system of claim 13, wherein each of the one ormore pairs of ultrasonic transducers is configured to operate in a pitchcatch mode in which the first ultrasonic transducer is configured toemit an acoustic wave and the second ultrasonic transducer is configuredto receive the acoustic wave.
 15. The system of claim 13, wherein themovable component comprises a ram of a BOP of the BOP stack assembly.16. The system of claim 13, wherein the one or more pairs of ultrasonictransducers comprise multiple pairs of ultrasonic transducers extendingalong a longitudinal axis of the body that is parallel to a direction ofmovement of the movable component.
 17. The system of claim 13, whereinthe one or more pairs of ultrasonic transducers comprise multiple pairsof transducers extending along an axial axis of the body that isperpendicular to a direction of movement of the movable component. 18.The system of claim 13, wherein the one or more pairs of transducerscomprise phased array transducers.
 19. A method for monitoring a blowoutpreventer (BOP) stack assembly, the method comprising using a processorto: provide a drive signal to cause a first transducer to emit anacoustic wave, wherein the first transducer is disposed on a first sideof a body configured to support a movable component of the BOP stackassembly and is configured to emit the acoustic wave toward acorresponding second transducer disposed on a second side of the body,opposite the first side; determine a position of the movable componentbased on whether the acoustic wave is received at the correspondingsecond transducer; and provide a displayed output indicative of theposition of the movable component.
 20. The method of claim 19, whereinthe movable component comprises a ram of a BOP of the BOP stackassembly.